Have a gander on net-a-porter at shoes. I'll be honest - I've been to couple weddings recently and some of the women have had dresses worth £££ and looked no better than anyone else however good shoes.... Worth the money IMO. A dress from high end high street which maybe you have tailored to you by dressmaker so it fits like a glove will be just as good.
I've been trying to think of boutiques in Manchester - there must be some but can't think of any! You could try House of Fraser and I'd go to Reiss if I wasn't worried about the cost. Hope you find that dress!